Reply To: graco 3900 loosing preasure

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Thanks Dan for the heads up.
I found that hitting the pump will get it back to building pressure by accident…..i got pissed and gave it a whack…..thing went right back to work.

Yesterday….had a small job to do.
Got the machine out.
Set a bucket of HOTLINE on the machine(it was half empty and already had a splash of water in it from the week before).
So….i got out my drill….with my stiring wand…..whipped the paint up a little….
Turned the ball valve to prime….
And my pressure was at 2250 PSI while priming…..never seen that before!!!
I normally spray at 1800 to 1900 PSI….it wouldn’t even push the paint.
so i turned the PSI up all the way….and it sprayed fine.
Finished the job.
As i was cleaning out the machine….i clean my machine every time i use it…every time.
I use water.
When the second bucket of water went in…..the pressure built back up like it normally does.
I turned it back down to 1850 PSI.
And it ran normal.

What do you think happened here……i think the paint was to thick.
Property owners wanted me to do some extra striping at this same location.
So I returned with a bucket SET FAST.
Splashed it with the same amount of water as i do with HOT LINE.
Turned the ball valve to prime.
Let it run.
Turned the valve to build pressure.
it went to 1900 PSI.
Worked perfect the rest of the day.

What do you think happened?

Any help here is greatly appreciated.


Piedmont Seal & Stripe